Electrical calculators
Every calculator is free, runs in your browser and needs no account. Each result shows its steps and the clause or table it used, for New Zealand and Australia. Most jobs start with the cable size calculator, which sizes a cable to AS/NZS 3008 and checks it against AS/NZS 3000.
GuidesLearnStandardsWorked examples and the clauses behind each result.
Sorted for all trades
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Cables
22 calculators- Cable sizeFind the smallest cable size that passes each check.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Voltage dropCalculate voltage drop on a cable run and check the limit.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Loop impedanceCheck earth fault loop impedance against the maximum Zs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Fault ratingCheck that a conductor can withstand the fault current.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Conduit fillCheck that a cable bundle fits in a conduit.AS/NZS 3008.1.2AS/NZS 3000
- Voltage riseCalculate voltage rise for embedded generation or PV.AS/NZS 4777.1AS/NZS 3008.1.2AS/NZS 3008.1.1
- Underground cableDepth of cover and separation for a buried cable.AS/NZS 3000
- Segregation and separationCheck what may share an enclosure and the separation.AS/NZS 3000
- Maximum circuit lengthLongest run that voltage drop and the fault loop allow.AS/NZS 3000AS/NZS 3008.1.2
- Simplified selectorRead the Appendix C device rating and voltage drop tables.AS/NZS 3000
- Minimum conductor sizeLook up the smallest conductor allowed for a circuit.AS/NZS 3000
- Imperial cableFind the device rating for an old imperial cable.AS/NZS 3000
- Comms cable selectorPick a comms cable and check the run length.No standard
- Aerial clearancesLook up aerial conductor clearances and spacing.AS/NZS 3000
- Site cord lengthThe longest a cord or cable may run on a construction site.AS/NZS 3012
- Loop power budgetCheck the voltage a 4–20 mA loop leaves the transmitter.AS/NZS 3008.1.2AS/NZS 3008.1.1
- DC cable sizeSize a d.c. cable up to 1500 V for current and voltage drop.AS/NZS 3008.1.1
- Correction factorsRead each correction factor and the rating a cable needs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Total voltage dropAdd the drop of mains, submain and final against 5 %.AS/NZS 3000AS/NZS 3008.1.2AS/NZS 3008.1.1
- Conductor coloursFind wire colours for fixed wiring and cords, old and new.AS/NZS 3000AS/NZS 3760
- Cable tray fillTray or ladder width, tiers, kg/m and the grouping factor.AS/NZS 3008.1
- Cable loss costWhat a cable size up saves in energy, cost and CO2.AS/NZS 3008.1
Protection
10 calculators- IDMT protectionPlot the trip curves of inverse-time overcurrent relays.IEC 60255IEEE C37.112
- RCD selectionCheck if an RCD is required and test the trip time.AS/NZS 3000Electricity (Safety) Regulations 2010
- Switchboard formCheck separation, access and clearances for a switchboard.AS/NZS 3000
- Circuit checkCheck an installed circuit: cable, device, drop and Zs.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- Fault level at a boardProspective fault current at a board from its source.AS/NZS 3008.1.2AS/NZS 3008.1.1AS/NZS 3000
- RCD arrangementCheck circuits per RCD and the lighting split.AS/NZS 3000
- Circuit chartMake a board circuit chart and the labels it needs.AS/NZS 3000
- RCD leakage budgetHow much standing leakage one RCD can carry.AS/NZS 3000AS/NZS 3760
- MCB trip curvePlot an MCB trip band against the cable it protects.AS/NZS 3000AS/NZS 3008.1.2AS/NZS 3008.1.1
- Surge protectionIs a surge protective device required or recommended here?AS/NZS 3000
Loads
15 calculators- Maximum demandEstimate maximum demand for domestic or non‑domestic loads.AS/NZS 3000 Table C1/C2
- Full load currentCalculate full load current from power, voltage and phase.No standard
- MotorFind motor full load current, starting current and torque.No standard
- BatteryCalculate battery bank capacity and autonomy for a load.No standard
- Circuit loadingCount the points a final subcircuit can carry.AS/NZS 3000
- Max demand by phaseSpread the load over three phases and see the imbalance.AS/NZS 3000
- Lighting lumen methodLuminaire count and grid for a room by the lumen method.AS/NZS 1680.1AS/NZS 1158.1.2
- EV charger circuitCheck EV chargers for spare capacity, cable size and RCD.AS/NZS 3000AS/NZS 3008.1.2AS/NZS 3008.1.1
- Power factor correctionFind the capacitor kvar to lift a power factor.AS/NZS 3000
- Max demand by floor areaEstimate commercial demand from floor area and use.AS/NZS 3000 Table C3
- Spare capacitySee if a new load fits the main switch of a supply.AS/NZS 3000 Cl 2.2.2
- Motor circuitCable, breaker, contactor and overload for one motor.AS/NZS 3000AS/NZS 3008.1.2AS/NZS 3008.1.1
- Motor starting methodsCompare DOL, star-delta, soft start and drive starts.No standard
- VSD motor leadCheck a drive’s motor lead: peak voltage, length and cable.AS/NZS 3000
- Load scheduleMaximum demand of a site’s boards by switchboard diversity.AS/NZS 3000
Power
12 calculators- Three phase powerConvert between power, current, voltage and power factor.No standard
- TransformerCalculate transformer full load current and impedance.No standard
- Generator currentFull load and fault current of a generator from its kVA.No standard
- Ohm's lawAny two of V, I, R and P give the other two.No standard
- Generator sizingSize a generator from a load list with motor starting.No standard
- Transformer inrushCheck a transformer’s switch-on inrush against its breaker.AS/NZS 3000
- Transformer sizingSize a transformer from the demand, with growth and losses.No standard
- UPS sizingSize a UPS and its battery for a run time.AS/NZS 3000
- Neutral currentThe neutral current of an unbalanced three‑phase load.AS/NZS 3000
- Voltage unbalanceVoltage or current unbalance from three line readings.No standard
- HarmonicsTHD, neutral current and K-factor from a spectrum.AS/NZS 3008.1AS/NZS 3000
- Battery duty cycleSize a stationary battery and charger to a duty cycle.No standard
Solar
5 calculators- PV string sizingModules per string, string current and isolator for PV.AS/NZS 5033AS/NZS 4777.2
- Home batterySize a home battery for the solar evening load.AS/NZS 5139
- PV array isolator and earthingRate the PV array cables, d.c. isolator and earthing.AS/NZS 5033AS/NZS 3000
- Battery location checkCheck where a home battery can go under AS/NZS 5139.AS/NZS 5139
- Battery arc flash and classBattery DVC, hazard class, arc flash energy and PPE level.AS/NZS 5139
Safety
8 calculators- Arc flashEstimate the energy of an arc flash and its PPE category.IEEE 1584-2018IEEE 1584-2002
- Construction site supplySupply, RCD and test rules for a construction site.AS/NZS 3012
- Show and carnival wiringShow wiring RCD checks, plus site wiring depth and height.AS/NZS 3002Electricity (Safety) Regulations 2010
- Wet area zonesFind the Section 6 zone, IP and RCD near water.AS/NZS 3000
- Obtrusive lightCheck outdoor light at a boundary window by AS/NZS 4282.AS/NZS 4282
- Downlight clearanceIC, CA90 or Non‑IC: may insulation touch the light?AS/NZS 3000
- Accessory locationPower points near a cooktop, gas cylinder, vent or sink.AS/NZS 3000
- IP ratingDecode an IP code and find the least for a location.AS 60529AS/NZS 3000
Testing
3 calculators- Test resultsCheck measured test results against Section 8 limits.AS/NZS 3000AS/NZS 3017Electricity (Safety) Regulations 2010
- Test and tagRetest intervals and pass limits for portable gear.AS/NZS 3760
- Test schedulePrint a board test sheet with the limit for each test.AS/NZS 3017AS/NZS 3000Electricity (Safety) Regulations 2010
Fire
4 calculators- Sounder levelFind the sound level a fire alarm system must reach.NZS 4512
- Fire alarm cablingLook up cable and circuit rules for fire alarm systems.NZS 4512
- Fire alarm batterySize the standby battery for a fire alarm panel.NZS 4512
- Detector spacingDetector spacing and count for a room or corridor.NZS 4512
Regulatory
3 calculators- Regulatory pathwayFind the paperwork for a job in NZ or Australia.Electricity (Safety) Regulations 2010
- Assessment intervalsRead the assessment interval reg 75 and NZS 4512 state.Electricity (Safety) Regulations 2010NZS 4512
- Hand-held supplyRead the supply arrangements regs 88 to 89A list.Electricity (Safety) Regulations 2010